Semisynthetic Ecdysteroid Cinnamate Esters and <i>tert</i>-Butyl Oxime Ether Derivatives with Trypanocidal Activity

The parasite <i>Trypanosoma cruzi</i> is the causative agent of Chagas disease, a neglected tropical disease that affects the lives of millions of indigenous people in Latin America. As medications to treat Chagas disease are limited to the application of benznidazole and nifurtimox, which are not ideal treatments for the chronic stage of the disease, the search for new antichagasic drug candidates is an important need. Ecdysone has previously been shown to interfere with the life cycle of <i>T. cruzi</i>. Here, we report the biological profiling and subsequent semisynthetic structure optimization of 47 ecdysteroids against <i>T. cruzi</i> with the aim of identifying selective trypanocidal ecdysteroids. Two moderately trypanocidal pharmacophores were identified: ecdysteroids containing a 6-<i>tert</i>-butyl oxime ether and a cinnamic ester moiety. These functional groups were combined into the structures of four new semisynthetic ecdysteroids (<b>44</b>-<b>47</b>), among which <b>44</b> exerted potent and selective trypanocidal activity (IC₅₀ < 2 μM). Cellular infection assays showed that ecdysteroid <b>44</b> potently and efficiently inhibited amastigote replication as determined by trypomastigote release after cellular infection with an IC₅₀ of 2.7 ± 0.1 μM. The compound was similarly potent to benznidazole (IC₅₀ = 3.8 ± 0.7 μM) and more than 5-fold more cytotoxic toward <i>T. cruzi</i> over RAW264.7 host macrophages. Overall, the ecdysteroid cinnamate ester <b>44</b> is a novel trypanocidal lead structure that needs to be further characterized in follow-up studies.